The goal of this renewal application for training support in the Postdoctoral Virology Training Program at The Wistar Institute and University of Pennsylvania, is to develop exceptional investigators schooled in the fundamentals of Virology. This will be achieved in the context of modem molecular biology, viral pathogenesis, immunology and structural biology in an environment that is well known for its legacy in vaccine development. We have established a strong postdoctoral training program whose faculty has been assembled from The Wistar Institute and University of Pennsylvania community. The trainers on this program are a closely knit group of 13 of the best (out of approximately 30) active research investigators in Virology who interact with the trainees and with each other. The program uses the facilities of the Wistar Institute, the Department of Microbiology in the School of Medicine, and the Department of Microbiology in the School of Dentistry at the University of Pennsylvania. Trainees are recruited through advertisements in Nature, Science, ASM News, or through letters to chairmen of Microbiology Departments in Medical Schools and direct application to mentors. Ethics training and minority recruitment performed at Wistar is coordinated with the biomedical graduate studies office of the University of Pennsylvania. There is one minority trainer in this program. The program is unique in the breadth and depth of researchers in Virology (and associated disciplines within the Wistar/Penn community) that it offers as mentors to trainees. Many DNA and RNA viruses are under study including DNA tumor viruses, animal and human herpes viruses, retroviruses including HIV, rhabdo and corona viruses. The disciplines involved in these studies include molecular biology, structural biology and immunology. Each trainer has independent funding and all have active research programs. Training is supplemented by seminars featuring invited virologists, symposia, as well as weekly research seminars within the individual laboratories. The training grant organizes a highly popular annual training symposium at which the trainees in each investigators laboratory present their work and the training grant camaraderie is established and maintained.